1. Field of Invention
The present invention relates to a continuously variable transmission (CVT) for motor vehicles, in particular for agricultural tractors.
2. Background of Prior Art
In the tractor field, transmissions are known in which a continuous control of speed is obtained, said transmissions being referred to as variable-speed drives or continuously variable transmissions (CVTs). In other words, in these transmissions the speed of the motor vehicle can be regulated, without any discontinuity, over the entire the range from the maximum speed of forward movement to the maximum speed of backward movement or maximum speed in reverse. In particular, there are known solutions in which the CVT comprises equipment for continuous variation of motion in terms of torque and of speed delivered. The continuous variation is obtained between two shafts and a differential by means of a first mechanical device with fixed transmission ratio and a second mechanical device with variable transmission ratio; set between the first device and the second device is an epicyclic gear train.
However, in the known solutions, the transmissions develop in the direction of the length of the motor vehicle, thus rendering them unsuitable for low-power tractors, in which there is, instead, the requirement of maximum compactness in a transverse direction.
The present invention, therefore, belongs within the aforesaid framework and leads to a series of advantages, which will emerge clearly from the contents of the ensuing detailed description, advantages which are linked, above all, to the extreme compactness of the transmission in a transverse direction.